/*
 * Author:
 *      Guido Draheim <guidod@gmx.de>
 *      Tomi Ollila <Tomi.Ollila@iki.fi>
 *
 * Copyright (c) 1999,2000,2001,2002,2003 Guido Draheim
 *          All rights reserved,
 *          use under the restrictions of the
 *          Lesser GNU General Public License
 *          or alternatively the restrictions
 *          of the Mozilla Public License 1.1
 */

#include <zzip_lib.h>                                         /* exported...*/
#include <zzip_file.h>

#include <string.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdlib.h>
#include <ctype.h>

#include <zzip_format.h>
#include <zzip_fetch.h>
#include <zzip___debug.h>

#if 0
    #if defined ZZIP_HAVE_IO_H
        #include <io.h> /* tell */
    #else
        #define tell(fd) lseek(fd, 0, SEEK_CUR)
    #endif
#else
    #define tells(fd) seeks(fd, 0, SEEK_CUR)
#endif

/**
 * the direct function of => zzip_close(fp). it will cleanup the
 * inflate-portion of => zlib and free the structure given.
 *
 * it is called quite from the error-cleanup parts
 * of the various => _open functions.
 *
 * the .refcount is decreased and if zero the fp->dir is closed just as well.
 */
int
zzip_file_close(ZZIP_FILE* fp)
{
    auto int self;
    ZZIP_DIR* dir = fp->dir;

    if (fp->method)
        inflateEnd(&fp->d_stream); /* inflateEnd() can be called many times */

    if (dir->cache.locked == NULL)
        dir->cache.locked = &self;

    if (fp->buf32k)
    {
        if (dir->cache.locked == &self &&
            dir->cache.buf32k == NULL) dir->cache.buf32k = fp->buf32k;
        else free(fp->buf32k);
    }

    if (dir->currentfp == fp)
        dir->currentfp = NULL;

    dir->refcount--;
    /* ease to notice possible dangling reference errors */
    memset(fp, 0, sizeof(*fp));

    if (dir->cache.locked == &self &&
        dir->cache.fp == NULL) dir->cache.fp = fp;
    else free(fp);

    if (dir->cache.locked == &self)
        dir->cache.locked = NULL;

    if (!dir->refcount) return zzip_dir_close(dir);else return 0;
}


static int
zzip_file_saveoffset(ZZIP_FILE* fp)
{
    if (fp)
    {
        __zzipfd fd = fp->dir->fd;
        zzip_off_t off = fp->io->fd.seeks(fd, 0, SEEK_CUR);
        if (off < 0)
            return -1;

        fp->offset = off;
    }
    return 0;
}

#ifndef ZZIP_CHECK_BACKSLASH_DIRSEPARATOR            /* NOTE: also default */
    #define ZZIP_CHECK_BACKSLASH_DIRSEPARATOR 0      /* to "NO" on win32 ! */
#endif

#if !defined strcasecmp && !defined ZZIP_HAVE_STRCASECMP
    #define ZZIP_CHECK_BACKSLASH_DIRSEPARATOR 1
#endif

#if !ZZIP_CHECK_BACKSLASH_DIRSEPARATOR + 0
    #define dirsep_strrchr(N, C) strrchr(N, C)
    #define dirsep_casecmp strcasecmp
#else
    #define dirsep_strrchr(N, C) _dirsep_strrchr(N)
    #define dirsep_casecmp _dirsep_casecmp
static zzip_char_t*
_dirsep_strrchr(zzip_char_t* name)
{
    char* n = strrchr(name, '/');
    char* m = strrchr(name, '\\');
    if (m && n && m > n) n = m;
    return n;
}
static int
_dirsep_casecmp(zzip_char_t* s1, zzip_char_t* s2)
{
    /* ASCII tolower - including mapping of backslash in normal slash */
    static const char mapping[] = "@abcdefghijklmnopqrstuvwxyz[/]^_";
    int c1, c2;
    while (*s1 && *s2)
    {
        c1 = (int)(unsigned char)*s1;
        c2 = (int)(unsigned char)*s2;
        if ((c1 & 0xE0) == 0x40) c1 = mapping[c1 & 0x1f];
        if ((c2 & 0xE0) == 0x40) c2 = mapping[c2 & 0x1f];
        if (c1 != c2)
            return (c1 - c2);
        s1++; s2++;
    }

    return (((int)(unsigned char)*s1) - ((int)(unsigned char)*s2));
}
#endif

static int zzip_inflate_init(ZZIP_FILE*, struct zzip_dir_hdr*);

/**
 * open an => ZZIP_FILE from an already open => ZZIP_DIR handle. Since
 * we have a chance to reuse a cached => buf32k and => ZZIP_FILE memchunk
 * this is the best choice to unpack multiple files.
 *
 * Note: the zlib supports 2..15 bit windowsize, hence we provide a 32k
 *       memchunk here... just to be safe.
 */
ZZIP_FILE*
zzip_file_open(ZZIP_DIR* dir, zzip_char_t* name, int o_mode)
{
    auto int self;
    zzip_error_t err = (zzip_error_t)0;
    struct zzip_file* fp = 0;
    struct zzip_dir_hdr* hdr = dir->hdr0;
    int (* cmp)(zzip_char_t*, zzip_char_t*);

    cmp = (o_mode & ZZIP_CASELESS) ? dirsep_casecmp : strcmp;

    if (!dir || !dir->fd || dir->fd == (unsigned)-1) return 0;

    if (o_mode & ZZIP_NOPATHS)
    {
        register zzip_char_t* n = dirsep_strrchr(name, '/');
        if (n) name = n + 1;
    }

    if (hdr)
        while (1)
        {
            register zzip_char_t* hdr_name = hdr->d_name;
            if (o_mode & ZZIP_NOPATHS)
            {
                register zzip_char_t* n = dirsep_strrchr(hdr_name, '/');
                if (n) hdr_name = n + 1;
            }

            HINT4("name='%s', compr=%d, size=%d\n",
                  hdr->d_name, hdr->d_compr, hdr->d_usize);

            if (!cmp(hdr_name, name))
            {
                switch (hdr->d_compr)
                {
                    case 0: /* store */
                    case 8: /* inflate */
                        break;
                    default:
                    { err = ZZIP_UNSUPP_COMPR; goto error; }
                }

                if (dir->cache.locked == NULL)
                    dir->cache.locked = &self;

                if (dir->cache.locked == &self &&
                    dir->cache.fp)
                {
                    fp = dir->cache.fp; dir->cache.fp = NULL;
                    /* memset(zfp, 0, sizeof *fp); cleared in zzip_file_close() */
                }
                else
                {
                    if (!(fp = (ZZIP_FILE*)calloc(1, sizeof(*fp))))
                    {
                        err = ZZIP_OUTOFMEM; goto error;
                    }
                }

                fp->dir = dir;
                fp->io = dir->io;
                dir->refcount++;

                if (dir->cache.locked == &self &&
                    dir->cache.buf32k)
                {
                    fp->buf32k = dir->cache.buf32k; dir->cache.buf32k = NULL;
                }
                else
                {
                    if (!(fp->buf32k = (char*)malloc(ZZIP_32K)))
                    {
                        err = ZZIP_OUTOFMEM; goto error;
                    }
                }

                if (dir->cache.locked == &self)
                    dir->cache.locked = NULL;
                /*
                 * In order to support simultaneous open files in one zip archive
                 * we'll fix the fd offset when opening new file/changing which
                 * file to read...
                 */

                if (zzip_file_saveoffset(dir->currentfp) < 0)
                {
                    err = ZZIP_DIR_SEEK; goto error;
                }

                fp->offset = hdr->d_off;
                dir->currentfp = fp;

                if (dir->io->fd.seeks(dir->fd, hdr->d_off, SEEK_SET) < 0)
                {
                    err = ZZIP_DIR_SEEK; goto error;
                }

                { /* skip local header - should test tons of other info,
                   * but trust that those are correct */
                    zzip_ssize_t dataoff;
                    struct zzip_file_header* p = (struct zzip_file_header*)fp->buf32k;

                    dataoff = dir->io->fd.read(dir->fd, (void*)p, sizeof(*p));
                    if (dataoff < (zzip_ssize_t)sizeof(*p))
                    {
                        err = ZZIP_DIR_READ;  goto error;
                    }
                    if (!zzip_file_header_check_magic(p)) /* PK\3\4 */
                    {
                        err = ZZIP_CORRUPTED; goto error;
                    }

                    dataoff = zzip_file_header_sizeof_tail(p);

                    if (dir->io->fd.seeks(dir->fd, dataoff, SEEK_CUR) < 0)
                    {
                        err = ZZIP_DIR_SEEK; goto error;
                    }

                    fp->dataoffset = dir->io->fd.tells(dir->fd);
                    fp->usize = hdr->d_usize;
                    fp->csize = hdr->d_csize;
                }

                err = (zzip_error_t)zzip_inflate_init(fp, hdr);
                if (err)
                {
                    goto error;
                }

                return fp;
            }
            else
            {
                if (hdr->d_reclen == 0)
                    break;
                hdr = (struct zzip_dir_hdr*)((char*)hdr + hdr->d_reclen);
            } /*cmp name*/
        } /*forever*/
    dir->errcode = ZZIP_ENOENT;         zzip_errno(ZZIP_ENOENT);
    return NULL;
error:
    if (fp) zzip_file_close(fp);
    dir->errcode = err;                 zzip_errno(err);
    return NULL;
}

/**
 *  call => inflateInit and setup fp's iterator variables,
 *  used by lowlevel => _open functions.
 */
static int
zzip_inflate_init(ZZIP_FILE* fp, struct zzip_dir_hdr* hdr)
{
    int err;
    fp->method = hdr->d_compr;
    fp->restlen = hdr->d_usize;

    if (fp->method)
    {
        memset(&fp->d_stream, 0, sizeof(fp->d_stream));

        err = inflateInit2(&fp->d_stream, -MAX_WBITS);
        if (err != Z_OK)
        {
            goto error;
        }

        fp->crestlen = hdr->d_csize;
    }
    return 0;
error:
    if (fp) zzip_file_close(fp);
    return err;
}

/**
 * This function closes the given ZZIP_FILE handle.
 *
 * If the ZZIP_FILE wraps a normal stat'fd then it is just that int'fd
 * that is being closed and the otherwise empty ZZIP_FILE gets freed.
 */
int
zzip_fclose(ZZIP_FILE* fp)
{
    if (!fp) return 0;
    if (!fp->dir)
    {
        int r = fp->io->fd.close(fp->fd); free(fp); return r;
    }                                                           /* stat fd */
    else return zzip_file_close(fp);
}

/** => zzip_fclose
 */
int
zzip_close(ZZIP_FILE* fp)
{
    return zzip_fclose(fp);
}

/**
 * This functions read data from zip-contained file.
 *
 * It works like => read(2) and will fill the given buffer with bytes from
 * the opened file. It will return the number of bytes read, so if the => EOF
 * is encountered you will be prompted with the number of bytes actually read.
 *
 * This is the routines that needs the => buf32k buffer, and it would have
 * need for much more polishing but it does already work quite well.
 *
 * Note: the 32K buffer is rather big. The original inflate-algorithm
 *       required just that but the latest zlib would work just fine with
 *       a smaller buffer.
 */
zzip_ssize_t
zzip_file_read(ZZIP_FILE* fp, char* buf, zzip_size_t len)
{
    ZZIP_DIR* dir;
    zzip_size_t l;
    zzip_ssize_t rv;

    if (!fp || !fp->dir) return 0;

    dir = fp->dir;
    l = fp->restlen > len ? len : fp->restlen;
    if (fp->restlen == 0)
        return 0;

    /*
     * If this is other handle than previous, save current seek pointer
     * and read the file position of `this' handle.
     */
    if (dir->currentfp != fp)
    {
        if (zzip_file_saveoffset(dir->currentfp) < 0
            || fp->io->fd.seeks(dir->fd, fp->offset, SEEK_SET) < 0)
        {
            dir->errcode = ZZIP_DIR_SEEK; return -1;
        }
        else
        {
            dir->currentfp = fp;
        }
    }

    /* if more methods is to be supported, change this to `switch ()' */
    if (fp->method)  /* method != 0   == 8, inflate */
    {
        fp->d_stream.avail_out = l;
        fp->d_stream.next_out = (unsigned char*)buf;

        do
        {
            int err;
            zzip_size_t startlen;

            if (fp->crestlen > 0 && fp->d_stream.avail_in == 0)
            {
                zzip_size_t cl = (fp->crestlen < ZZIP_32K ?
                                  fp->crestlen : ZZIP_32K);
                /*  zzip_size_t cl = fp->crestlen > 128 ? 128 : fp->crestlen; */

                zzip_ssize_t i = fp->io->fd.read(dir->fd, fp->buf32k, cl);
                if (i <= 0)
                {
                    dir->errcode = ZZIP_DIR_READ;  /* or ZZIP_DIR_READ_EOF ? */
                    return -1;
                }
                fp->crestlen -= i;
                fp->d_stream.avail_in = i;
                fp->d_stream.next_in = (unsigned char*)fp->buf32k;
            }

            startlen = fp->d_stream.total_out;
            err = inflate(&fp->d_stream, Z_NO_FLUSH);

            if (err == Z_STREAM_END)
            {
                fp->restlen = 0;
            }
            else
            if (err == Z_OK)
            {
                fp->restlen -= (fp->d_stream.total_out - startlen);
            }
            else
            {
                dir->errcode = err; return -1;
            }
        }
        while (fp->restlen && fp->d_stream.avail_out);

        return l - fp->d_stream.avail_out;
    }
    else
    {
        /* method == 0 -- unstore */
        rv = fp->io->fd.read(dir->fd, buf, l);
        if (rv > 0)
        {
            fp->restlen -= rv;
        }
        else
        if (rv < 0)
        {
            dir->errcode = ZZIP_DIR_READ;
        }
        return rv;
    }
}

/**
 * This function will read(2) data from a real/zipped file.
 *
 * the replacement for => read(2) will fill the given buffer with bytes from
 * the opened file. It will return the number of bytes read, so if the EOF
 * is encountered you will be prompted with the number of bytes actually read.
 *
 * If the file-handle is wrapping a stat'able file then it will actually just
 * perform a normal => read(2)-call, otherwise => zzip_file_read is called
 * to decompress the data stream and any error is mapped to => errno(3).
 */
zzip_ssize_t
zzip_read(ZZIP_FILE* fp, char* buf, zzip_size_t len)
{
    if (!fp) return 0;
    if (!fp->dir)
    {
        return fp->io->fd.read(fp->fd, buf, len);
    }                                               /* stat fd */
    else
    {
        register zzip_ssize_t v;
        v = zzip_file_read(fp, buf, len);
        if (v == -1)
        {
            errno = zzip_errno(fp->dir->errcode);
        }
        return v;
    }
}

/** => zzip_read
 */
zzip_size_t
zzip_fread(void* ptr, zzip_size_t size, zzip_size_t nmemb, ZZIP_FILE* file)
{
    if (!size) size = 1;
    return zzip_read(file, (char*)ptr, size * nmemb) / size;
}


#define ZZIP_WRONLY O_WRONLY
#define ZZIP_EXCL O_EXCL

#if     defined                 O_SYNC
    #define ZZIP_SYNC O_SYNC
#else
    #define ZZIP_SYNC 0
#endif

#if     defined                 O_NONBLOCK
    #define ZZIP_NONBLOCK O_NONBLOCK
#elif   defined                 O_NDELAY
    #define ZZIP_NOCTTY O_NDELAY
#else
    #define ZZIP_NOCTTY 0
#endif

/* ------------------------------------------------------------------- */

/**
 * This function will => fopen(3) a real/zipped file.
 *
 * It has some magic functionality builtin - it will first try to open
 * the given <em>filename</em> as a normal file. If it does not
 * exist, the given path to the filename (if any) is split into
 * its directory-part and the file-part. A ".zip" extension is
 * then added to the directory-part to create the name of a
 * zip-archive. That zip-archive (if it exists) is being searched
 * for the file-part, and if found a zzip-handle is returned.
 *
 * Note that if the file is found in the normal fs-directory the
 * returned structure is mostly empty and the => zzip_read call will
 * use the libc => read to obtain data. Otherwise a => zzip_file_open
 * is performed and any error mapped to => errno(3).
 *
 * unlike the posix-wrapper => zzip_open the mode-argument is
 * a string which allows for more freedom to support the extra
 * zzip modes called ZZIP_CASEINSENSITIVE and ZZIP_IGNOREPATH.
 * Currently, this => zzip_fopen call will convert the following
 * characters in the mode-string into their corrsponding mode-bits:
 *  <ul><li><code> "r" : O_RDONLY : </code> read-only
 * </li><li><code> "b" : O_BINARY : </code> binary (win32 specific)
 * </li><li><code> "f" : O_NOCTTY : </code> no char device (unix)
 * </li><li><code> "i" : ZZIP_CASELESS : </code> inside zip file
 * </li><li><code> "*" : ZZIP_NOPATHS : </code> inside zip file only
 * </ul> all other modes will be ignored for zip-contained entries
 * but they are transferred for compatibility and portability,
 * including these extra sugar bits:
 *  <ul><li><code> "x" : O_EXCL :</code> fail if file did exist
 * </li><li><code> "s" : O_SYNC :</code> synchronized access
 * </li><li><code> "n" : O_NONBLOCK :</code> nonblocking access
 * </li><li><code> "z#" : compression level :</code> for zlib
 * </li><li><code> "g#" : group access :</code> unix access bits
 * </li><li><code> "u#" : owner access :</code> unix access bits
 * </li><li><code> "o#" : world access :</code> unix access bits
 * </ul>... the access bits are in traditional unix bit format
 * with 7 = read/write/execute, 6 = read/write, 4 = read-only.
 *
 * The default access mode is 0664, and the compression level
 * is ignored since the lib can not yet write zip files, otherwise
 * it would be the initialisation value for the zlib deflateInit
 * where 0 = no-compression, 1 = best-speed, 9 = best-compression.
 */
ZZIP_FILE*
zzip_fopen(zzip_char_t* filename, zzip_char_t* mode)
{
    return zzip_freopen(filename, mode, 0);
}

/** => zzip_fopen
 *
 * This function receives an additional argument pointing to
 * a ZZIP_FILE* being already in use. If this extra argument is
 * null then this function is identical with calling => zzip_fopen
 *
 * Per default, the old file stream is closed and only the internal
 * structures associated with it are kept. These internal structures
 * may be reused for the return value, and this is a lot quicker when
 * the filename matches a zipped file that is incidently in the very
 * same zip arch as the old filename wrapped in the stream struct.
 *
 * That's simply because the zip arch's central directory does not
 * need to be read again. As an extension for this function, if the
 * mode-string contains a "q" then the old stream is not closed but
 * left untouched, instead it is only given as a hint that a new
 * file handle may share/copy the zip arch structures of the old file
 * handle if that is possible, i.e when they are in the same zip arch.
 */
ZZIP_FILE*
zzip_freopen(zzip_char_t* filename, zzip_char_t* mode, ZZIP_FILE* stream)
{
    int o_flags = 0;
    int o_modes = 0664;
    if (!mode) mode = "rb";

    #ifndef O_BINARY
    #define O_BINARY 0
    #endif
    #ifndef O_NOCTTY
    #define O_NOCTTY 0
    #endif
    #ifndef O_SYNC
    #define O_SYNC 0
    #endif
    #ifndef O_NONBLOCK
    #define O_NONBLOCK 0
    #endif

    for (; *mode; mode++)
    {
        switch (*mode)
        {
            case '0': case '1': case '2': case '3': case '4':
            case '5': case '6': case '7': case '8': case '9':
                continue; /* ignore if not attached to other info */
            case 'r': o_flags |= mode[1] == '+' ? O_RDWR : O_RDONLY; break;
            case 'w': o_flags |= mode[1] == '+' ? O_RDWR : O_WRONLY;
                o_flags |= O_TRUNC; break;
            case 'b': o_flags |= O_BINARY; break;
            case 'f': o_flags |= O_NOCTTY; break;
            case 'i': o_modes |= ZZIP_CASELESS; break;
            case '*': o_modes |= ZZIP_NOPATHS; break;
            case 'x': o_flags |= O_EXCL; break;
            case 's': o_flags |= O_SYNC; break;
            case 'n': o_flags |= O_NONBLOCK; break;
            case 'o': o_modes &= ~07;
                o_modes |= ((mode[1] - '0')) & 07; continue;
            case 'g': o_modes &= ~070;
                o_modes |= ((mode[1] - '0') << 3) & 070; continue;
            case 'u': o_modes &= ~0700;
                o_modes |= ((mode[1] - '0') << 6) & 0700; continue;
            case 'q': o_modes |= ZZIP_FACTORY; break;
            case 'z': /* compression level */
                continue; /* currently ignored, just for write mode */
        }
    }

    {
        ZZIP_FILE* fp =
            zzip_open_shared_io(stream, filename, o_flags, o_modes, 0, 0);

        if (!o_modes & ZZIP_FACTORY && stream)
            zzip_file_close(stream);

        return fp;
    }
}

/**
 * This function will => open(2) a real/zipped file
 *
 * It has some magic functionality builtin - it will first try to open
 * the given <em>filename</em> as a normal file. If it does not
 * exist, the given path to the filename (if any) is split into
 * its directory-part and the file-part. A ".zip" extension is
 * then added to the directory-part to create the name of a
 * zip-archive. That zip-archive (if it exists) is being searched
 * for the file-part, and if found a zzip-handle is returned.
 *
 * Note that if the file is found in the normal fs-directory the
 * returned structure is mostly empty and the => zzip_read call will
 * use the libc => read to obtain data. Otherwise a => zzip_file_open
 * is performed and any error mapped to => errno(3).
 *
 * There was a possibility to transfer zziplib-specific openmodes
 * through o_flags but you should please not use them anymore and
 * look into => zzip_open_ext_io to submit them down. This function
 * is shallow in that it just extracts the zzipflags and calls <ul><li><code>
 * zzip_open_ext_io(filename, o_flags, zzipflags|0664, 0, 0) </code></li></ul>
 * you must stop using this extra functionality (not well known
 * anyway) since zzip_open might be later usable to open files
 * for writing in which case the _EXTRAFLAGS will get in conflict.
 *
 * compare with  => open(2) and => zzip_fopen
 */
ZZIP_FILE*
zzip_open(zzip_char_t* filename, int o_flags)
{
    /* backward compatibility */
    int o_modes = 0664;
    if (o_flags & ZZIP_CASEINSENSITIVE)
    {
        o_flags ^= ZZIP_CASEINSENSITIVE; o_modes |= ZZIP_CASELESS;
    }
    if (o_flags & ZZIP_IGNOREPATH)
    {
        o_flags ^= ZZIP_IGNOREPATH;      o_modes |= ZZIP_NOPATHS;
    }
    return zzip_open_ext_io(filename, o_flags, o_modes, 0, 0);
}

/* ZZIP_ONLYZIP won't work on platforms with sizeof(int) == 16bit */
#if ZZIP_SIZEOF_INT + 0 == 2
    #undef ZZIP_ONLYZIP
#endif

/** => zzip_open
 *
 * This function uses explicit ext and io instead of the internal
 * defaults, setting them to zero is equivalent to => zzip_open
 *
 * note that the two flag types have been split into an o_flags
 * (for fcntl-like openflags) and o_modes where the latter shall
 * carry the zzip_flags and possibly accessmodes for unix filesystems.
 * Since this version of zziplib can not write zipfiles, it is not
 * yet used for anything else than zzip-specific modeflags.
 */
ZZIP_FILE*
zzip_open_ext_io(zzip_char_t* filename, int o_flags, int o_modes,
                 zzip_strings_t* ext, zzip_plugin_io_t io)
{
    return zzip_open_shared_io(0, filename, o_flags, o_modes, ext, io);
}

/** => zzip_open
 *
 * This function takes an extra stream argument - if a handle has been
 * then ext/io can be left null and the new stream handle will pick up
 * the ext/io. This should be used only in specific environment however
 * since => zzip_file_real does not store any ext-sequence.
 *
 * The benefit for this function comes in when the old file handle
 * was openened from a file within a zip archive. When the new file
 * is in the same zip archive then the internal zzip_dir structures
 * will be shared. It is even quicker, as no check needs to be done
 * anymore trying to guess the zip archive place in the filesystem,
 * here we just check whether the zip archive's filepath is a prefix
 * part of the filename to be opened.
 *
 * Note that this function is also used by => zzip_freopen that
 * will unshare the old handle, thereby possibly closing the handle.
 */
ZZIP_FILE*
zzip_open_shared_io(ZZIP_FILE* stream,
                    zzip_char_t* filename, int o_flags, int o_modes,
                    zzip_strings_t* ext, zzip_plugin_io_t io)
{
    if (stream && stream->dir)
    {
        if (!ext) ext = stream->dir->fileext;
        if (!io) io = stream->dir->io;
    }
    if (!io) io = zzip_get_default_io();

    if (o_modes & (ZZIP_PREFERZIP | ZZIP_ONLYZIP)) goto try_zzip;
try_real:
    /* prefer an existing real file */
    {
        zzip_plugin_io_t os = (o_modes & ZZIP_ALLOWREAL)
                              ?  zzip_get_default_io() : io;
        __zzipfd fd = os->fd.open(filename, o_flags); /* io->fd.open */
        if (fd != (unsigned)-1)
        {
            ZZIP_FILE* fp = (ZZIP_FILE*)calloc(1, sizeof(ZZIP_FILE));
            if (!fp)
            {
                os->fd.close(fd); return 0;
            }                                        /* io->fd.close */

            fp->fd = fd;
            fp->io = os;
            return fp;
        }
        if (o_modes & ZZIP_PREFERZIP) return 0;
    }
try_zzip:

    /* if the user had it in place of a normal xopen, then
     * we better defend this lib against illegal usage */
    if (o_flags & (O_CREAT | O_WRONLY))
    {
        errno = EINVAL; return 0;
    }
    if (o_flags & (O_RDWR))
    {
        o_flags ^= O_RDWR; o_flags |= O_RDONLY;
    }

    /* this is just for backward compatibility -and strictly needed to
     * prepare ourselves for more options and more options later on... */
    /*# if (o_modes & ZZIP_CASELESS) { o_flags |= ZZIP_CASEINSENSITIVE; } */
    /*# if (o_modes & ZZIP_NOPATHS)  { o_flags |= ZZIP_IGNOREPATH; } */

    /* see if we can open a file that is a zip file */
    { char basename[PATH_MAX];
      char* p;
      strcpy(basename, filename);

      /* see if we can share the same zip directory */
      if (stream && stream->dir && stream->dir->realname)
      {
          zzip_size_t len = strlen(stream->dir->realname);
          if (!memcmp(filename, stream->dir->realname, len) &&
              filename[len] == '/' && filename[len + 1])
          {
              ZZIP_FILE* fp =
                  zzip_file_open(stream->dir, filename + len + 1, o_modes);
              if (!fp)
              {
                  errno = zzip_errno(stream->dir->errcode);
              }
              return fp;
          }
      }

      /* per each slash in filename, check if it there is a zzip around */
      while ((p = strrchr(basename, '/')))
      {
          zzip_error_t e = (zzip_error_t)0;
          ZZIP_DIR* dir;
          ZZIP_FILE* fp;
          int fd;

          *p = '\0'; /* cut at path separator == possible zipfile basename */
          fd = __zzip_try_open(basename, o_flags | O_RDONLY | O_BINARY, ext, io);
          if (fd == -1)
          {
              continue;
          }
          /*    found: */
          /* found zip-file, now try to parse it */
          dir = zzip_dir_fdopen_ext_io(fd, &e, ext, io);
          if (e)
          {
              errno = zzip_errno(e); io->fd.close(fd); return 0;
          }

          /* (p - basename) is the lenghtof zzip_dir part of the filename */
          fp = zzip_file_open(dir, filename + (p - basename) + 1, o_modes);
          if (!fp)
          {
              errno = zzip_errno(dir->errcode);
          }
          else
          {
              if (!dir->realname) dir->realname = strdup(basename);
          }

          zzip_dir_close(dir);
          /* note: since (fp) is attached that (dir) will survive */
          /* but (dir) is implicitly closed on next zzip_close(fp) */

          return fp;
      } /*again*/

      if (o_modes & ZZIP_PREFERZIP) goto try_real;
      errno = ENOENT; return 0; }
}

#if defined ZZIP_LARGEFILE_RENAME && defined EOVERFLOW && defined PIC
    #undef zzip_open_shared_io /* zzip_open_shared_io64 */
    #undef zzip_open_ext_io /* zzip_open_ext_io64 */
    #undef zzip_opendir_ext_io /* zzip_opendir_ext_io64 */

_zzip_export
ZZIP_FILE * zzip_open_shared_io(ZZIP_FILE* stream,
                                zzip_char_t* name, int o_flags, int o_modes,
                                zzip_strings_t* ext, zzip_plugin_io_t io);
_zzip_export
ZZIP_FILE * zzip_open_ext_io(zzip_char_t* name, int o_flags, int o_modes,
                             zzip_strings_t* ext, zzip_plugin_io_t io);
_zzip_export
ZZIP_DIR * zzip_opendir_ext_io(zzip_char_t* name, int o_modes,
                               zzip_strings_t* ext, zzip_plugin_io_t io);

/* DLL compatibility layer - so that 32bit code can link with this lib too */

_zzip_export
ZZIP_FILE * zzip_open_shared_io(ZZIP_FILE* stream,
                                zzip_char_t* name, int o_flags, int o_modes,
                                zzip_strings_t* ext, zzip_plugin_io_t io)
{
    if (!io) return zzip_open_shared_io64(stream, name, o_flags, o_modes,
                                          ext, io);
    errno = EOVERFLOW; return NULL;
}

_zzip_export
ZZIP_FILE * zzip_open_ext_io(zzip_char_t* name, int o_flags, int o_modes,
                             zzip_strings_t* ext, zzip_plugin_io_t io)
{
    if (!io) return zzip_open_ext_io64(name, o_flags, o_modes, ext, io);
    errno = EOVERFLOW; return NULL;
}

_zzip_export
ZZIP_DIR * zzip_opendir_ext_io(zzip_char_t* name, int o_modes,
                               zzip_strings_t* ext, zzip_plugin_io_t io)
{
    if (!io) return zzip_opendir_ext_io64(name, o_modes, ext, io);
    errno = EOVERFLOW; return NULL;
}

#endif /* ZZIP_LARGEFILE_RENAME && EOVERFLOW && PIC */

/* ------------------------------------------------------------------- */

/**
 * This function will rewind a real/zipped file.
 *
 * It seeks to the beginning of this file's data in the zip,
 * or the beginning of the file for a stat'fd.
 */
int
zzip_rewind(ZZIP_FILE* fp)
{
    ZZIP_DIR* dir;
    int err;

    if (!fp)
        return -1;

    if (!fp->dir)
    { /* stat fd */
        fp->io->fd.seeks(fp->fd, 0, SEEK_SET);
        return 0;
    }

    dir = fp->dir;
    /*
     * If this is other handle than previous, save current seek pointer
     */
    if (dir->currentfp != fp)
    {
        if (zzip_file_saveoffset(dir->currentfp) < 0)
        {
            dir->errcode = ZZIP_DIR_SEEK; return -1;
        }
        else
        {
            dir->currentfp = fp;
        }
    }

    /* seek to beginning of this file */
    if (fp->io->fd.seeks(dir->fd, fp->dataoffset, SEEK_SET) < 0)
        return -1;

    /* reset the inflate init stuff */
    fp->restlen = fp->usize;
    fp->offset = fp->dataoffset;

    if (fp->method)
    { /* method == 8, deflate */
        err = inflateReset(&fp->d_stream);
        if (err != Z_OK)
        {
            goto error;
        }

        /* start over at next inflate with a fresh read() */
        fp->d_stream.avail_in = 0;
        fp->crestlen = fp->csize;
    }

    return 0;

error:
    if (fp) zzip_file_close(fp);
    return err;
}

/**
 * This function will perform a => lseek(2) operation on a real/zipped file
 *
 * It will try to seek to the offset specified by offset, relative to whence,
 * which is one of SEEK_SET, SEEK_CUR or SEEK_END.
 *
 * If the file-handle is wrapping a stat'able file then it will actually just
 * perform a normal => lseek(2)-call. Otherwise the relative offset
 * is calculated, negative offsets are transformed into positive ones
 * by rewinding the file, and then data is read until the offset is
 * reached.  This can make the function terribly slow, but this is
 * how gzio implements it, so I'm not sure there is a better way
 * without using the internals of the algorithm.
 */
zzip_off_t
zzip_seek(ZZIP_FILE* fp, zzip_off_t offset, int whence)
{
    zzip_off_t cur_pos, rel_ofs, read_size, ofs;
    ZZIP_DIR* dir;

    if (!fp)
        return -1;

    if (!fp->dir)
    { /* stat fd */
        return fp->io->fd.seeks(fp->fd, offset, whence);
    }

    cur_pos = zzip_tell(fp);

    /* calculate relative offset */
    switch (whence)
    {
        case SEEK_SET: /* from beginning */
            rel_ofs = offset - cur_pos;
            break;
        case SEEK_CUR: /* from current */
            rel_ofs = offset;
            break;
        case SEEK_END: /* from end */
            rel_ofs = fp->usize + offset - cur_pos;
            break;
        default: /* something wrong */
            return -1;
    }

    if (rel_ofs == 0)
        return cur_pos; /* don't have to move */

    if (rel_ofs < 0)
    { /* convert backward into forward */
        if (zzip_rewind(fp) == -1)
            return -1;

        read_size = cur_pos + rel_ofs;
        cur_pos = 0;
    }
    else
    {
        /* amount to read is positive relative offset */
        read_size = rel_ofs;
    }

    if (read_size < 0) /* bad offset, before beginning of file */
        return -1;

    if (read_size + cur_pos > (zzip_off_t)fp->usize) /* bad offset, past EOF */
        return -1;

    if (read_size == 0) /* nothing to read */
        return cur_pos;

    dir = fp->dir;
    /*
     * If this is other handle than previous, save current seek pointer
     * and read the file position of `this' handle.
     */
    if (dir->currentfp != fp)
    {
        if (zzip_file_saveoffset(dir->currentfp) < 0
            || dir->currentfp->io->fd.seeks(dir->fd, fp->offset, SEEK_SET) < 0)
        {
            dir->errcode = ZZIP_DIR_SEEK; return -1;
        }
        else
        {
            dir->currentfp = fp;
        }
    }

    if (fp->method == 0)
    { /* unstore, just lseek relatively */
        ofs = fp->io->fd.tells(dir->fd);
        ofs = fp->io->fd.seeks(dir->fd, read_size, SEEK_CUR);
        if (ofs > 0)
        { /* readjust from beginning of file */
            ofs -= fp->dataoffset;
            fp->restlen = fp->usize - ofs;
        }
        return ofs;
    }
    else
    {
        /* method == 8, inflate */
        char* buf;
        /*FIXME: use a static buffer! */
        buf = (char*)malloc(ZZIP_32K);
        if (!buf) return -1;

        while (read_size > 0)
        {
            zzip_off_t size = ZZIP_32K;
            if (read_size < size /*32K*/) size = read_size;

            size = zzip_file_read(fp, buf, (zzip_size_t)size);
            if (size <= 0)
            {
                free(buf); return -1;
            }

            read_size -= size;
        }

        free(buf);
    }

    return zzip_tell(fp);
}

/**
 * This function will => tell(2) the current position in a real/zipped file
 *
 * It will return the current offset within the real/zipped file,
 * measured in uncompressed bytes for the zipped-file case.
 *
 * If the file-handle is wrapping a stat'able file then it will actually just
 * perform a normal => tell(2)-call, otherwise the offset is
 * calculated from the amount of data left and the total uncompressed
 * size;
 */
zzip_off_t
zzip_tell(ZZIP_FILE* fp)
{
    if (!fp)
        return -1;

    if (!fp->dir)   /* stat fd */
        return fp->io->fd.tells(fp->fd);

    /* current uncompressed offset is uncompressed size - data left */
    return (fp->usize - fp->restlen);
}

/*
 * Local variables:
 * c-file-style: "stroustrup"
 * End:
 */